Abstract
We examined the contribution and distribution of wild-origin chinook salmon (Oncorhynchus tshawytcha) in the Salmon River, New York, during the 2005 spawning run. To determine the origin of each fish, we used scale metrics and a recently developed discriminant function model. We estimated that approximately 32% (∼20,000 individuals) of chinook salmon were of wild-origin and that there was a greater proportion of wild fish in younger age groups than in older groups (age-1 = 48.6%, age-2 = 47.2%, and age-3 = 21.1%). We also observed spatial differences in the distribution of wild- and hatchery-derived fish, with a higher proportion of wild-origin chinook salmon in the lower section of the river (47.5%) than in the upper sections (28.2%). The lowest proportion of wild fish was found in the Salmon River hatchery (12.4%), located in the upper section of the river. These findings suggest that wild-origin fish were more evenly distributed along the river, whereas hatchery fish were more likely to reach the upper parts of the river or enter the hatchery.